Glenn E Hemmerle waited for midnight. Then he would do something he'd never done before.

He checked his watch, for the fourth time. It was still 11:40.

The butterflies in Hemmerle's stomach were circling. He was, after all chairman and chief executive of Crown Books, one of America's largest book chains, and tonight he was setting a publishing first.

At the stroke of 12, he would open the doors of Crown branches all over the country and invite the American public in to buy the hottest book in the world, just seconds into its official day of publication. They had printed 2.5 million of them, all in hardback - the largest print run for any novel ever.

The store would stay open all night, but Hemmerle and his staff were ready. He had piles of the books, their covers gleaming. The Chamber, they declared. And above the title, two much more important words: John Grisham.

'He's really the only author we'd even attempt something like this with,' said Hemmerle, addressing a reporter from a British paper with a name he couldn't remember? What was it? The Guardian? 'His appeal, it's phenomenal...'

John Grisham is a rock star. The all-night opening, like the full-page newspaper ads or the TV campaign, are proof that he can sell a book the way Madonna sells a record. He doesn't have readers, he has fans.

Like the faithful who lined up at 12.01am to buy The Chamber, in time to get the free T-shirt that came with the first 50 copies sold. 'He's one terrific writer,' beamed Mary Ann Rodgers, a lawyer who had come to the Washington branch of Crown at a quarter to twelve. 'I may not get any sleep tonight,' said Jon Anderson. 'You can't put it down,' said Raymond Brown, 'you always want to read one more chapter.'

The publishing industry has never seen anything like it. Just three years ago, no one had heard of Grisham, a Mississippi lawyer who wrote stories on legal pads in his spare time. Since then he has topped the bestsellers' list four times. The sales figures are staggering. In America alone, The Firm sold 12 million in paperback, The Pelican Brief 11 million, A Time To Kill nine million. The Client sold three million copies in hardback, and the softcover has added another six million since its release this spring. At this rate, one bright spark worked out, by the year 2000 every novel sold in the US will be by John Grisham.

Walk along any beach or down the aisle of any train or plane: in 30 languages and countless reprints, he is there, in big, embossed letters. Hollywood has piled on the glory, too, bestowing on Grisham an unprecedented compliment. With the release this summer of The Client, starring Susan Sarandon and Tommy Lee Jones, the 39-year old author will have seen three of his legal suspense thrillers made into blockbuster movies, all within a single year. Universal Pictures paid him $3.5 million for The Chamber before they had read - and before he had written - a word.

Now he is number 31 on Forbes magazine's list of the Top 40 biggest earners in entertainment, just below Clint Eastwood and above Dustin Hoffman. The magazine estimated that the author bagged $25 million in 1992-3. This annoys him: he earned much, much more.

'They didn't get close,' says the remarkably handsome Mr Grisham, giving a clear-eyed smile. He is tanned, wearing impeccable chinos, a blue cotton shirt and a bristly layer of stubble. Give him an earring, and he could be the head of a high-earning ad agency. Without it, he's like the dashing young-ish lawyer you would find in a country town, a man with whom men would play squash and for whom women would betray their husbands.

He won't give his precise income, because he fears his two children, a 10-year-old boy and an eight-year-old girl, could be targets of a kidnapping - like something out of a Grisham novel. But how has he done it? How has Grisham become one of that tiny club of mega-authors, alongside Tom Clancy, Stephen King and Michael Crichton (ranked 20, 26 and 34 respectively on the Forbes Top 40)?

For some, this is the greatest John Grisham mystery of all. Reviewers who find his work eminently putdownable struggle to see what all the fuss is about. 'Written in the grand tradition of the American comic book,' one sneered. Even his admirers are hard pushed to explain Grisham's trick. 'If I knew the answer, every book I handled would be a major bestseller,' says his agent, Jay Garon. 'Part of what makes a phenomenon is that it can't be completely explained,' says his editor, David Gernert.

Grisham thinks there's no big secret. People were tired of the eighties sex 'n' shopping novel - 'Women's books,' he calls them. 'There was a void in the menu of commercial fiction for a new, young, American, male suspense writer. The timing was just perfect.'

His extra advantage, the booksellers say, is that Grisham has unusually broad appeal. Men read Clancy, women read Krantz but both read Grisham. There's so little sex in the books that parents and children can give them as gifts to each other.

He has also tapped into an American obsession which has spawned a whole genre: the law. The nation which gave the world LA Law, and soaks up 24-hour Court TV, has a large appetite for tales of justice done and justice denied. Scott Turow had a monster hit with Presumed Innocent and newcomer Steve Martini is already making a name in the same field. 'We hate lawyers, but we love stories about 'em,' says Grisham, with a smooth southern bend in his voice that is more Al Gore than Boss Hogg. His readers can't get enough.

'There's a natural conflict there of protagonist and antagonist, that produces a kind of drama that's always interesting,' muses Jon Anderson, one of those who queued up at midnight to buy The Chamber.

It is a peculiarly American fixation, this fascination with courts and those who fill them. Americans sue their doctors, their lawyers, even their parents. Grisham thinks it goes back to the constitution: 'We have all these rights that we're born with and "If you mess around with my rights, I'll sue you".'

Grisham is making a good living from that national litigiousness, crafting a formula which, so far, has not let him down: the lone, principled lawyer - usually young and/or inexperienced - in combat with darker, larger forces. In The Firm the Mafia and the Feds were chasing a freshly hired attorney; in The Pelican Brief a corporate giant and a corrupt president hunted down a female law student; now, in The Chamber, it is the Ku Klux Klan and scheming southern politicians who stand in the way of another, just-qualified lawyer.

Use the word 'formula' and most writers wince, but not Grisham. He is first and foremost not an auteur but the chairman and chief executive of John Grisham, Inc. He regards his work not as a canon, or an oeuvre, but a business. He talks about how long he's been selling books, not writing them. Ask the literary questions, about the role of the novel or the place of reading in this TV age, and his answers are usually platitudinous. But get him on to his royalties, and he is able to rattle off precise sales figures, his exact share (a dollar per book on the paperback, more on the hardback) and the details of his contracts. Like a businessman; like a lawyer.

This makes him refreshingly unpretentious. 'This is not art. This is not serious literature. My writing style is very simple, there's nothing fancy. I get from point A to point B. I can't write as well as some people; my talent is in coming up with good stories about lawyers. That's what I'm good at.'

Critics have never understood this simple point about him, he complains. He admits he is no intellectual - in the acknowledgements to The Chamber he confesses, 'I despise research' - yet the reviewers slate him, he says, for not matching up to their standards. 'A lot of them are frustrated novelists who can't get published, and here I am making umpteen zillion bucks a year.'

While literary authors tell you that a novel germinates when a character starts to gnaw away in their head, Grisham's begin when he gets an idea for a plot. Literary authors say they often don't know where their characters will take them. Grisham writes a 45-page outline, with two paragraphs per chapter explaining precisely what will happen next. Literary authors speak of the location of their novels acting as a 'force' or an 'extra character'. Ask if the Deep South carries a similar weight in his books and Grisham is succinct: 'Nah. They could be anywhere.'

The businessman-author admits that if he thinks a story will not have mass commercial appeal he won't write it. Perhaps it is this pragmatism which has insulated Grisham from the most commonly-heard observation about him. 'I like his books,' people say, 'but the films are crap.' Most readers who saw The Firm and The Pelican Brief came away deflated.

It is odd that his stories have made such an uneasy transition to the screen, especially when they often read like teleplays - complete with before-the-adverts cliffhangers at the end of each chapter. His books are free of interior monologues, complex character development, extraneous detail and sub-plot. They are all-action, fast-paced thrillers (although the latest book has plenty of more thoughtful moments, and is a clear attempt by Grisham to write something more substantial). They should make perfect cinema.

That they have not is more surprising still, when you hear Grisham say that he often has the future movie in mind when he's writing for the printed page. He'd only written half The Pelican Brief when a studio bought it and from then on, Grisham admits, he was writing a main character that looked and spoke like Julia Roberts. For his latest, The Chamber, he sees Paul Newman as the former Klansman sentenced to death for a 1960s race killing, and Brad Pitt as his lawyer-grandson.

'I've not been disappointed, but I've not been terribly thrilled either,' he says diplomatically about the films. He then points out quickly that he has nothing to do with the movie-making process, bar the odd dinner with the director, that he refuses invitations to Hollywood every day and that films come and go in a month, while a book lasts forever. He's making this point, about his distance from the whole business, when there's a knock on the door. He walks across the vast suite at the Manhattan hotel where he's based for this two-day promotional swing, to greet a bell-boy carrying two bottles of champagne. They are a gift from a TV company.

Like another Southern boy who made good recently, John Grisham was born in Arkansas, to poor, rural stock. Not 'hungry, dirty' poor, you understand, but poor all the same. His father was a sharecropper until young John was six, when one bad season after another finally forced the Grishams off the land.

They travelled across the South, wherever there was work, two conservative Baptists and their five children. 'We didn't know we were poor, we were just kids having a ball,' Grisham says, cheerily.

The lad was bright enough to get himself into local state college and from there to local law school. Even now, despite his private jet and worldwide book sales, Grisham has never spent more than 10 days outside the American South, let alone the United States.

He qualified in 1981, and established a small country practice in Southaven, Mississippi. Now he could get on with achieving the ambition that had propelled him to be a lawyer in the first place. 'I was very hungry to make money,' he says, fiddling with his antique watch. 'Not from a point of greed but from a point of wanting to be secure. I don't know if it goes back to my childhood or what, but it was a burning desire to succeed.'

Then, in 1983, he ran as a Democrat and won a seat in the Mississippi state legislature. Instead of a programme, he had dreams of higher office, perhaps as governor or a senator. But he soon realised politics was a 'dead-end street. You can starve in politics if you're honest. There's just no money there.'

Grisham says he became politicised as an attorney, often representing workers against big corporations, and some of that remains in his fiction. It is the ideology of 'the little guy' battling it out against the powers that be. More recently, the politics has gained a higher profile. He has been to the White House twice, once for a private viewing of The Pelican Brief, sharing a bucket of popcorn with Bill and Hillary. (As with every other Arkansan, it turns out that John Grisham is a cousin of the president's; seems Bill Clinton's grandfather was a Grisham.)

He's attended Democratic fund-raisers and he's even had flak from critics of the new book for writing a leftist 'treatise' against the death penalty. A self-described political junkie, he will not be enticed back in to the fray: 'You couldn't give me a seat in the US Senate, even with a big fat salary.'

Who can blame him? The plain fact is that John Grisham is living a charmed life. He and his strikingly attractive childhood sweetheart, Renee, live on a 70-acre farm in Oxford, Mississippi, a university town which has both rural peace and culture. He describes his estate as a place he never wants to leave: 'It has lots of space, lots of fresh air and no people.'

He writes early in the morning till after lunch, then plays with his kids or rides on his tractor. He is the best-selling author in the world, and can do whatever he likes in Hollywood. He makes more money than a minor eastern European country.

He is handsome, had a happy childhood and has never come close to real failure. As a result, he will never write the great American novel, but he does not care. In the plain, utterly transparent language favoured by his characters, he says it just as it is: 'I am the luckiest guy in the world.'